Two imidazolium-based surface-active ionic liquids with aromatic counterions, namely, 1-dodecyl-3-methylimidazolium salicylate (C(12)mimSal) and 1-dodecyl-3-methylimidazolium 3-hydroxy-2-naphthoate (C(12)mimHNC), were synthesized, and their aggregate behavior in aqueous solutions was systematically explored. Surface tension and conductivity measurements indicate that both C(12)mimSal and C(12)mimHNC show superior surface activity compared to the common imidazolium-based SAIL with the same hydrocarbon chain length, 1-dodecyl-3-methylimidazolium bromide (C(12)mimBr). This result demonstrates that the incorporation of aromatic counterions favors the formation of micelles. C(12)mimHNC displays a higher surface activity than C(12)mimSal, resulting from the different hydrophobicities of the counterions. In comparison with C(12)mimBr, C(12)mimSal not only can form hexagonal liquid-crystalline phase (H-1) in aqueous solution, but also exhibits a broad region of cubic liquid-crystalline phase (V-2) at higher concentration. As for the C(12)mimHNC/H2O system, a lamellar liquid-crystalline (La) phase was observed. These lyotropic liquid crystals (LLCs) were characterized by polarized optical microscopy (POM) and small-angle X-ray scattering (SAXS). Structural parameters calculated from SAXS patterns suggest that a higher concentration of the SAIL leads to a denser arrangement whereas a higher temperature results in the opposite effect. The rheological results manifest that the formed H-1 phase in the C(12)mimSal/H2O system exhibits an impressive viscoelastic behavior, indicated by a modulus (G' and G '') that is 1 order of magnitude higher than that of C(12)mimBr. Density functional theory (DFT) calculations reveal that C(12)mimSal has a more negative interaction energy with a water molecule and the Sal- counterion presents a stronger electronegativity than the HNC- counterion. The specific phase behavior of the C(12)mimSal/H2O and C(12)mimHNC/H2O systems can be attributed to the strong synergic interaction between the imidazolium cation and the aromatic counterion, including electrostatic attraction, hydrophobic interaction, and especially pi-pi interaction.